The present invention relates to a method of working a metal in which the microstructure of the body is rendered fine to thereby enhance the strength, ductility or homogeneity thereof; a metal body obtained by the metal working method; and a metal-containing ceramic body obtained by the metal working method.
It is well known that the microstructure of the metal-containing material, such as a metal body or a metal-containing ceramic, is rendered fine by means of ECAP (Equal-Channel Angular Pressing) to thereby enhance the strength or ductility of the material.
With ECAP, as shown in FIG. 19, an insertion passage 200 is formed with preset bending angle in the middle of a mold 100. A metal body 300 to be processed is pressed and inserted into the insertion passage 200, thereby the metal body 300 is bent along the insertion passage 200, and the shearing stress is generated in the metal body 300 due to the bending, thus the shearing stress makes the microstructure fine. The reference numeral 400 in FIG. 19 represents the plunger of the metal body.
In such ECAP, in order to make the body 300 bend easily along the insertion passage 200, the mold 100 is heated up to a preset temperature, thereby the whole metal body 300 is heated and accordingly the deformation resistance thereof is reduced. However, if the deformation resistance of the metal body 300 is greatly reduced, unwanted deformation will occur in the metal body 300, thus the heating temperature of the metal body 300 must be limited in a required minimum range.
Furthermore, while heating the metal body 300 as described above, it is necessary to use much more power to press the plunger 400, thus there will be some problems such as the deterioration of processing property. A method of working metal material and the device thereof is disclosed in Japanese patent publication No. 2001-321825, in which a solution is proposed as follows: locally heating the shear deformation zone of the passage applying the shear stress on the metal body in order to reduce the deformation resistance of the shear deformation region of the metal body, therefore, it can reduce the power needed during pressing the plunger, thus to improve the processing property.
Furthermore, when the shear deformation zone is heated, the metal having passed the shear deformation zone still maintains a preset heating temperature, therefore the deformation resistance of the whole metal body pushed outside of the insertion passage is reduced. If the metal body is continuously passed through the insertion passage, for the sake of the shearing stress acting repeatedly, it must take enough time to cool the metal body under the preset temperature so as to increase the deformation resistance.
Therefore, it is very hard to perform the treatment by the ECAP method in less than cooling time continuously, thus a problem of low productivity occurs.
With the ECAP, it is necessary to insert the metal body into the bending insertion passage. Therefore, there is a problem that it is very difficult to render the microstructure of a portion of the metal body fine.
Furthermore, in the method of making a portion of the microstructure of the metal body fine, for example, disclosed in Japanese patent publication No. 11-51103, a probe provided at an end of the rotor along the axis thereof is made to closely contact with the required position and to press the metal body. The grain refinement of the metal is performed by the friction with the probe through rotor rotating.
Nonetheless, the method using the friction with the probe is difficult to realize the treatment with a high efficiency, therefore, there is a same problem in that the productivity is very low as the case of using the ECAP method.
On the other hand, it is known that a method of mass manufacturing the metal body with the grain refinement microstructure is disclosed in Japanese patent publication No. 11-323481, in which low carbon steel or low carbon alloy steel with preset components is processed by decreasing the cross-section area 60% or more during the cooling course from high temperature.
However, the metal body which can be processed by using aforesaid method is only restricted to the low carbon steel or low carbon alloy steel with special components. Therefore, there is a problem in that the metal body with other components cannot use this method.
As stated above, during the process for forming of the metal body with high strength or high ductility by making the microstructure fine, the advantages and the disadvantages are existed concurrently. At present, such kind of metal is only used for special purpose without caring for the manufacturing cost, such as a luxury car or a fighter plane etc.
Under these circumstances, especially in vehicle industry, it is desired to reduce the bodywork weight in order to optimize the burnup or improve the driveability. Thereby, there is a huge demand, not only for luxury car, but also for ordinary car, that the weight reduction must be realized by using the metal body with high strength or high ductility through making the microstructure fine. Accordingly, a huge potential demand exists for a cheap metal body with high strength or high ductility.
In view of such actual state, the present inventor has proceeded research and development to work out the present invention. It is an object to provide a metal body or metal-containing ceramic body with high strength or high ductility which can be continuously formed during the process for making the microstructure fine so that it is possible to improve the productivity, and obtain a metal body or metal-containing ceramic body with low cost.